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CARDIAC MUSCLE

CARDIAC MUSCLE. OBJECTIVES At the end of this lecture you should be able to know types of cardiac muscle and its anatomical location. Arrangement of myofilaments and sarcoplasmic reticulum Steps involved in Contraction Functional differences. CARDIAC MUSCLES.

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CARDIAC MUSCLE

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  1. CARDIAC MUSCLE OBJECTIVES At the end of this lecture you should be able to know types of cardiac muscle and its anatomical location. • Arrangement of myofilaments and sarcoplasmic reticulum • Steps involved in Contraction • Functional differences

  2. CARDIAC MUSCLES • Cardiac muscle is found only in heart. • Shape = Rectangular shape.Short branched cells • Diameter = 20um Length = 100 um • Single nucleus • Regeneration of cardiac muscle fiber is controversial.Recent studies suggest that cardiac muscle cells have mild proliferative property.

  3. Cardiac muscle • Thick myosin filaments. • Thin actin filaments (Troponin present) • Striated appearance. • T-Tubule system associated with calcium loaded sarcoplasmicretculum. • Contraction occurs by sliding filament mechanism.

  4. Intercalated Disks • Structures between adjacent cells. • Myofibrils attached to desmosomes. • Gap junctions present.

  5. Input influencing Cardiac muscle contractile activity. 1. Sinoatrial node (SA node-Pacemaker) Location=Superior posterolateral wall of right atrium. Hormones. Neurotransmitters

  6. EXCITATION CONTRACTION COUPLING IN CARDIAC MUSCLE

  7. Sources of Cytosolic Calcium • L-Type calcium channels (modified DPR) (L= long lasting current )—Cardiac muscle cannot under go tetanic contractions. • ECF calcium 1.Depolarization of plasma membrane. 2.Slight Increase in cytosolic Ca 3.Triggers release of Ca from SR. • Rynaodine receptors (Ca channels)

  8. Thin filament activation • Cross- bridge cycling • Force generation • Same as SKELETAL MUSCLE

  9. Action Potential in Cardiac Muscle.

  10. Steps involved in contraction of Cardiac muscle

  11. Contraction ends • Cytosolic Ca conc is restored Ca-ATPase pumps Na/Ca countertranspoters

  12. Contraction ends • Cytosolic Ca conc is restored. Ca-ATPase activity Na/Ca countertranspoters

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